1. Field of the Invention
The present invention relates to a technique of utilizing a master slice approach and, more particularly, to a method of forming a semiconductor integrated circuit or large scale integration (LSI) circuit by forming each circuit pattern by units of a functional block on a semiconductor chip, using the master slice approach.
2. Description of the Related Art
The master slice approach is one of the fixed wiring approaches based on "LSI on slice" approach. In the master slice approach, a common pattern formed by means of a diffusion process (a transistor pattern, called a basic cell, in the form of a constant, i.e., fixed, arrangement) is prepared, and then, a wiring pattern is applied to the common pattern configured in accordance with the forms of the LSI or the specification or conditions demanded by a user. Therefore, a desired LSI can be constituted by designing and forming the wiring pattern in various ways. In constituting the desired LSI, two kinds of aluminium (Al) wiring pattern masks and two kinds of contact hole pattern masks are generally employed. Note, a first contact hole (hereinafter indicated by reference NA) effects a connection between a conduction region of a functional element, such as a transistor formed on the substrate, and a first Al wiring pattern (hereinafter indicated by reference LA), and a second contact hole (hereinafter indicated by reference NB) effects a connection between the first Al wiring pattern LA and a second Al wiring pattern (hereinafter indicated by reference LB).
Namely, a known typical master slice approach comprises the steps of forming fixed transistor patterns and forming a programmable wiring pattern. The latter step requires four processes of forming first contact holes NA in a first insulation layer formed on the substrate, forming thereon a first wiring pattern LA, forming second contact holes NB in a second insulation layer formed thereon, and forming thereon a second wiring pattern LB. In this case, each pattern employed in each of the four processes must be changed in accordance with user's demands or the forms of the LSI. This leads to a complication of the process and a prolongation of the designing period, and thus is not preferable. Accordingly, it would be preferable to decrease the number of the processes requiring a change or programming based on the user's demands, from a viewpoint of the reduction of the turnaround time and the simplification of the entire process.